Vehicles utilizing an internal combustion engine using a gasoline or heavy fuel oil as a main fuel have seriously polluted air. Accordingly, in order to reduce the pollution, great efforts are being made to develop an electric vehicle or a hybrid vehicle recently.
The electric vehicle is the vehicle using a battery engine operated by electric energy outputted from a battery. Because this electric vehicle uses the battery, in which a number of secondary batteries capable of charging and discharging are formed in a single pack, as a main power source, the electric vehicle brings great advantages such as no exhaust gases and very little noise.
On the other hand, the hybrid vehicle is the vehicle in the middle stage of the vehicle using an internal combustion engine and the electric vehicle, and uses power sources in at least two ways, for example, the internal combustion engine and the battery engine. Currently, the mixed type of hybrid vehicle which uses the internal combustion engine and a fuel cell directly obtaining electric energy by having a chemical reaction while continuously supplying hydrogen and oxygen or uses the battery and the fuel cell, etc. is being developed.
Like this, in the vehicle using the battery engine, the number of the secondary battery is increased in order to improve the power source. Since a number of connected cells directly influence the performance of the vehicle, as well as the performance of each battery cell must be superior, a battery management system (hereinafter, BMS) capable of efficiently managing the charge and discharge and the life for each of battery cells by measuring a voltage for each of battery cells, a total battery voltage and current, etc. is required.
In particular, the BMS calculates the SOC of the battery, stores it, calculates charge/discharge output which can be used to the vehicle according to the state of the battery and provides it to a vehicle controller and the like. However, due to the replacement of such a high voltage battery or the BMS, the last calculated SOC is not stored when detaching, and thus the real SOC of the battery and the SOC recognized by the battery management system will not be matched.
Like this, if the SOC of the battery is erroneously recognized, by calculating and controlling the charge/discharge output of the vehicle based on the erroneous SOC information, over-discharge or over-charge can be occurred.